Machine translation (MT) is the automatic translation from a first language (a “source” language) into another language (a “target” language). Systems that perform an MT process are said to “decode” the source language into the target language.
A statistical MT system that translates foreign language sentences, e.g., French, into English may include the following components: a language model that assigns a probability P(e) to any English string; a translation model that assigns a probability P(f|e) to any pair of English and French strings; and a decoder. The decoder may take a previously unseen sentence f and try to find the e that maximizes P(e|f), or equivalently maximizes P(e)*P(f|e).
Compounded words may present a challenge for MT systems. Compounding of words is common in a number of languages (e.g., German, Dutch, Finnish, and Greek). An example of a compounded word is the German word “Aktionsplan”, which was created by joining the words “Aktion” and “Plan”. Words may be joined freely in such languages, which may greatly increase the vocabulary size of such languages.